Flicker Detection CDS Circuit for Low-Light Image Sensors
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Solution Overview
Problem
Current correlated double sampling (CDS) circuits in CMOS image sensors face challenges in enhancing detection sensitivity in low illumination environments and effectively managing flicker noise from light sources like fluorescent lighting.
Innovation Solution
A flicker detection (FD) circuit with a FD CDS circuit and FD ADC is introduced, utilizing switches and capacitors to amplify and offset flicker pixel signals, and an FFT circuit to analyze frequency domains, enabling improved flicker detection and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional CDS circuits are used in CMOS image sensors, then basic noise removal is achieved, but detection sensitivity in low illumination environments is insufficient and flicker noise from light sources cannot be effectively managed
Solution Approach 1:
The pixel array is divided into first and second regions, with different pixel types (first pixels and second pixels) having different output configurations. First pixels output both image signals and flicker signals, while second pixels output only flicker signals. This segmentation allows dedicated flicker detection pathways that improve sensitivity to flicker noise while maintaining basic noise removal capabilities through conventional CDS circuits.
Solution Approach 2:
A flicker detection circuit is introduced as an intermediary component between the pixel array and the output stage. This circuit receives flicker signals from second pixels and performs dedicated flicker detection, acting as a mediator that specifically targets flicker noise removal while preserving the conventional CDS functionality for general noise management.
2Reliability
If conventional CDS circuits are used, then common noise components are removed through subtraction of analog values, but the complexity of the circuit increases when attempting to enhance detection sensitivity and manage flicker noise
Solution Approach 1:
First pixels are designed with multi-functionality, outputting both image signals for conventional CDS processing and flicker signals for dedicated flicker detection. This universal pixel design allows a single pixel type to serve multiple purposes, reducing the need for entirely separate circuit pathways and thereby limiting the increase in overall circuit complexity while enhancing noise reduction effectiveness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances detection sensitivity and accurately identifies flicker noise, improving image sensor performance in low light conditions by effectively filtering out common noise components and optimizing signal amplification.
Implementation Method 1
a pixel array having a plurality of pixels configured to convert an optical signal into an electrical signal
Implementation Method 2
Correlated double sampling (CDS) circuits may be used to increase detection sensitivity in low illumination environments. CDS circuits may subtract an analog value, which is input when there is light or when there is no light, thereby removing a common noise component.
Implementation Method 3
the FD CDS circuit being configured to receive a flicker pixel signal output from at least one pixel, summate with an output offset signal, and amplify the summation based on a gain to form a flicker detection signal
Data Source
AI summary
A flicker detection circuit is provided. The flicker detection circuit may include a flicker detection correlated double sampling (FD CDS) circuit including first to sixth switches turned on or off based on a control signal, and first to fourth capacitors, the FD CDS circuit being configured to receive a flicker pixel signal output from at least one pixel, summate with an output offset signal, and amplify the summation based on a gain to form a flicker detection signal; and an analog-to-digital converter (ADC) configured to quantize the flicker detection signal.